Originally Posted by
cyccommute
Pushing the plunger down into the ground is far easier than trying to pump at 90° to the wheel.
That's a skill thing (but it's ok if you can't learn it, different strokes etcetera, I know otherwise competent cyclists who are lost without indexed shifting); and pumps that have hoses have more places to leak.
As well, you can exert more force on the air column in the pump with it held between your hands than you can pushing down on the ground.